Tappet construction



1958 E. A. THOMPSON TAPPET CONSTRUCTION Filed Dec. 5, 1955 INVENTO'R. THOMPSON BY 4.4 6490 ATTORNEYS.

TAPPET CONSTRUCTION Earl A. Thompson, Ferndale, Mich. Application December 5, 1955, Serial No. 550,924 Claims. (Cl. 123-90) This invention relates to a tappet and more particularly to a hydraulic tappet.

A hydraulic tappet, or a valve lifter, as it is sometimes called, is an element adapted to be located between an operators, such as a cam on a shaft driven by an internal combustion engine and a push rod for operating the poppet valves of the engine. This invention in primarily concerned with improvements in the construction of such tappets.

it is an object of this invention to provide a tappet of the hydrauplic type that is designed so that a minimum of wear occurs between the moving parts thereof.

Another object of the invention is to provide a tappet of the above described type that is designed so that oil within the tappet may be utilized for' lubricating the rocker arm assembly.

In the drawing:

Fig. l is a view partly in section showing a portion of an internal combustion engine with a tappet of this invention.

Fig. 2 is a longitudinal sectional view llustrated in Fig. 1.

Fig. 3 is a sectional view taken along the lines 3-3 in Fig. 2.

Referring to the drawing, there is shown in Fig. 1 a portion of an engine including a cam shaft having cams 12 thereon and an engine block 14 provided with an oil conduit 16 having branch passageways 18 communicating with bores 20. Within each bore 20, there is slidably arranged a tappet 22 of this invention. A rocker arm 24 for operating the valves of the engine, not shown, is actuated by tappet 22 through a push rod 26.

Referring now to Fig. 2, it will be observed that tappet 22 includes an outer body portion 28 generally in the form of a cylindrical member which is open at its upper end and has a base 30 closing its lower end. Base 30 is preferably made of cast iron and is united to the lower end of body 28 by welding as at 32. The manner in which the base 30 is welded to the lower end of body 28 is described in my application Serial No. 446,497, filed July 29, 1954.

Body 28 is preferably formed from a length of seamof the tappet less steel tubing and is fashioned such as to provide a restriction 34 at the central portion thereof and a second restriction 36 at the open upper end of the body. These restrictions are in the nature of zones of reduced diameter. The inner face of base 30 is machined with a centrally located, generally conically-shaped socket 38 in which the lower end of a cylinder 40 is seated. Cylinder 40 has an outside diameter such as to provide clearance with the inner walls of body 28. Within cylinder 4t), there is arranged a hollow piston 42, the bore 44 of which comunicates with a passageway 46 in an extension 48 at the lower end of the piston. The open lower end of passageway 46 is controlled by a check valve in the form of a ball 50 biased to seat against and close the end of passageway 46 by means of a helical spring 52, The

space between the lower ends of piston 42 and cylinder 40 defines an oil chamber 53 into which the admission of oil is controlled by ball check 50. [Piston 42 and cylinder 40 are detachably connected for relative operating movement by a spring ring 54. Ring .54 is seated in an annular groove 55 at the upper end of cylinder 40 and engages with a reduced portion 56 adjacent the upper end of piston 42, The reduced portion 56 is defined by a shoulder 58 at its upper end and a shoulder 68 at its lower end. A cap 62 is telescoped over the upper end of piston 40 and is detachably connected therewith by means of a split ring 64 seated in an annular groove 66 adjacent the lower end of cap 62. The details of this split ring connection between the piston 42 and the cylinder 40 on the one hand and between the piston 42 and the cap 62 on the other hand is described in my application Serial No. 405,088, filed January 20, 1954.

Cap 62 is provided with a blind bore 68 which forms an extension of the bore 44 of piston 42. Adjacent its lower end, cap 62 is fashioned with a shoulder 70 which engages with the upper end of piston 42. Bore 68 communicates with the interior of body 28 by means of a radial passageway 72 extending through the side Wall of cap 62. At its upper end, cap 62 is formed with a generally semi-spherical seat 74 for the reception of the lower end of push rod 26. At the lower end of seat 7 3, there is formed an axial passageway 76 which communicates with a radial passageway 78. Cap 62 slidably engages the side wall of body 28 at the restricted end 36 thereof. However, the tolerances between the outer diameter of cap 62 and the inner diameter of body 28 at the restriction 36 is such that there is a clearance between these members of between .0007" and .0015".

Push rod 26 comprises a hollow tube having generally semi-spherical ends, the lower end being provided with an opening 80 and the upper end with an opening 82. The upper end of push rod 26 engages with a semispherical shaped seat 84 at one end of rocker arm 24.

Referring now to Fig. 3, it will be seen that the upper end 36 of body 28 is flattened at one side thereof as indicated at 86. This flattened portion may be fashioned by simply striking the end of body 28 while it is retained in the die and has a suitable mandrel inserted therein of a desired shape. Cap 62 is formed of steel and has a flat face 88 machined at one side thereof so as to slidably engage with the inner face of the fiat portion 86 at the end of body 28.

In operation, oil under pressure from the lubricating system of the engine flows through conduit 16 and branch passageway 13 into the space 90 that is provided between the side wall of bore 20 in the engine block and restriction 34 at the central portion of the tappet. This oil flows into the tappet body 28 through the opening 92 and fills the interior of the tappet body. The oil is free to flow through opening 72 into the bores 68 and 44 of the cap 62 and piston 42, respectively. Since this oil is under pressure, it flows through passageway 46, unseats ball 5th and fills oil chamber 53. As the cam 12 lifts the tappet, the oil in chamber 53 is subjected to compression, thusclosing the ball check 58 and transmitting thrust from the member 40 to the piston 42. This thrust is transmitted through cap 62 and. by the push rod 26 to the rocker arm 24. in view of the clearance between the outer surface of cap 62 and the inner surface of body 28 at the restricted zone 36 thereof, a portion of the pressurized oil in body 28 escapes through this clearance space and passes through passageways 76 and 725 through the opening 80 and upwardly into hollow push rod 26. The pressure of this oil as it escapes through this clearance space is reduced; but nevertheless, it is sufficient to rise in the hollow push rod 26 and flow outwardly therefrom at the spherical seat 84 of the A rocker arm 24. Thus, this oil is utilized for lubricating the connection between the push rod and the rocker arm. The rocker arm is provided with a passageway 94 extending from they spherical seat 84. to the bearing member as on which the rocker arm is pivoted. There fore, the whole rocker arm. assembly is oiled in this manner.

As is. conventional, cam 12.-is designed. to'engage base 3% of body- 28 off center. This tends to. rotatebody 23. if cap 62 were permitted to rotatefreely in body 2?, considerable'amount ofwear would occur between the contacting, surfaces. of piston. 42. and cylinder 40 and to a'lesser extent betweerrcap 62 and body 23..

However, by forming body 28 and cap 62, withthe. ill-.-

terengaged. fiatside Wall portions 86 and 38,1135}? aty, relative. rotation of these. members is. prevented and Wear is. maintained at a minimum. Evenwith this con-- struction, however, it has been found that there is a. slight amount vofrelativev rotation. between piston. 42. and cylinder 4%; probably because of vibration and the axial inclination of the load applied. by push rod 26. This has been found desirablesince it tends. to. equalize the very slight wear between piston 42..and cylinder id.

I claim:

1. A hydraulic tappet comprising a generally cylin drical hollow body having an open end and a base at the closed endthereof adapted to be engaged by a cam to actuate. said tappet, a cylinder in said body having a.

closed end and havingan open end extending in the direction of theopenend of the body, a piston slidably disposed in said cylinder and having one end projecting outwardly thereof, a cap on said projecting end of said piston slidably engagingthe wall of said body ad" jacent the open end thereof, means on said body through which pressurized oil can .be admitted into said body and from the interior of said body to said piston-cylinder assembly, said cap having at the outer end thereof means forming a seat for the reception of one end of a push rod and means for directing a small portion of the oil in said body to said seat in saidcap, said last mentioned means comprising a passageway in said cap extending from said seat to the surface of the cap that is slidably engaged with said body adjacent the open end of the body, there being a slight clearance provided between said slidably engaged surfaces;

2. In an internal combustion engine of the type having poppet valves operated by a rocker arm assembly, the

combination of means forminga bore in the engine a hollow tappet body slidably arranged in said bore, said body having a piston-cylinder assembly therein, said assembly havingan end portion projecting out one end of the body, said endportion having a seat therein, a tubular push rod, extending from said seat to and engaged with said rocker armassembly, whereby when said tappet is aetuated,.the valves are operated through said push rod and rocker arm assembly, means for admitting pressurized oil to said bore, said body having an aperture therein communicating with said bore to admit pressurized oil to the interior thereof, means for bypassing a small portion of the oil within said body to said seat, said push rod being open at its opposite ends, whereby said oil conducted to said seat is permitted to rise through said push rod'to lubricate said rocker arm 4. The combination called for in claim 3,wh ereinsaid rocker arm assembly includes a passageway communicating with the open end of. the push, rod with whichitis;

associated.

5.. A hydraulic tappet comprising a generally cylin drical hollow body having an open end and a base at the-: closed end thereof adapted to be engaged by a cam toactuate said tappet, a cylinder in said body having a closed.

end andhaving an open end extending in the direction of theopen end of the body, a piston slidably disposed in said cylinder and having one end projecting outward,

ly thereofla cap on. said projecting end. of. said: piston slidably and non-rotatably engaging the, wall of saidbody adjacent the open end thereof, means on said body through which pressurized oil can be, admittedinto said body and from the interior of said body to said pistoncylinder assembly, said cap having at the outer end thereof means forming a seat for the reception of one end of a push rod and means for directing a small-portion of the oil in said body, to saidseat in said cap, said last mentioned means comprising a passage-way in said:

cap extending from said seat to the surface of the cap that is slidably engaged with said body adjacent. the open end of the. body, there being a slight. clearance provided'between said slidably engaged surfaces.

References Cited in the tile of this patent UNITED. STATES PATENTS 

